This invention pertains to refractory compositions, particularly such compositions suitable for gunning.
Gun mixes have been long known, and when they were first developed it was the practice to use conventional refractory bonds, for example sodium silicate or magnesium sulfate, as the bonding agent. However, gun mixes have different requirements from other refractory compositions. For example, they must mix readily with water, adhere well to a furnace wall without slumping or rebounding, and they must set to a coherent mass very rapidly.
Accordingly, special bonding systems, particularly combination bonds, have been developed for gun mixes. For example, U.S. Pat. No. 3,357,842 discloses a bonding system using monosodium phosphate, U.S. Pat. No. 3,357,843 discloses bonding using glassy polyphosphates, and U.S. Pat. No. 3,879,208 discloses a bonding system using aluminum sulfate.
Combination bond systems have also been used with other types of refractory compositions. For example, U.S. Pat. No. 2,619,426 discloses a refractory composition suitable for ramming, casting, pressing, or use as a mortar and bonded with a combination of aluminum sulfate and calcium phosphate. Also, it is known to make an air-set mortar from calcined clay, brick grog, and raw kyanite bonded with about 12% clay, 8% aluminum sulfate, and 4% dry sodium phosphate.
The present invention is directed to a phosphate-containing bonding system for refractory gun mixes, one which provides a more versatile mix with better water range and in which any alkali metal phosphate bond can be used with predictable results. The use of such phosphate-containing bonding system provides low temperature strength, as opposed to a ceramic bond, in the mix.